function animate(obj, target,callback) {
    clearInterval(obj.timer);

    obj.timer = setInterval(function () {
        let step =(target - obj.offsetLeft) / 10;
        step = step > 0 ? Math.ceil(step) : Math.floor(step) ; 
        if (obj.offsetLeft == target) {
            clearInterval(obj.timer);
            if(callback){
                callback();
            }
        }
        obj.style.left = obj.offsetLeft + step + 'px';
    }, 15)
}